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DESICCANT TYPE AIR DRYERS

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  • INSTRUCTION MANUAL

    CDH SERIES

    PRESSURE-SWING

    DESICCANT TYPE

    COMPRESSED

    AIR DRYERS

    SERVICE DEPARTMENT : (724) 746-1100

    Contents

    1. GENERAL SAFETY INFORMATION ................................ 22. RECEIVING, MOVING, UNPACKING .............................. 23. DESCRIPTION ................................................................. 34. INSTALLATION ................................................................. 85. CONTROLLERS GENERAL .......................................... 166. CONTROLLER TIMER BASED ..................................... 187. CONTROLLER LEVEL 1 ............................................... 208. CONTROLLER LEVEL 2 ............................................... 319. OPERATION ..................................................................... 4810. MAINTENANCE ............................................................... 5411. TROUBLESHOOTING ..................................................... 5512. NOTES ............................................................................. 56 WARRANTY ..................................................................... 60

    3162265 Rev. B 4/07XX-XXX-X

    Internal Use Only

    3162258b / 070417

    MODELS

    RATEDFLOW

    REFERAS

    MODELS

    CDHESERIESw/ TimerController

    CDHLSERIES

    w/ Level 1Controller

    CDHTSERIES

    w/ Level 2Controller

    CDHE-40CDHE-60CDHE-90

    CDHL-40CDHL-60CDHL-90

    CDHT-40CDHT-60CDHT-90

    40 SCFM60 SCFM90 SCFM

    406090

    CDHE-115CDHE-165CDHE-260

    CDHL-115CDHL-165CDHL-260

    CDHT-115CDHT-165CDHT-260

    115 SCFM165 SCFM260 SCFM

    115165260

    CDHE-370CDHE-450CDHE-590

    CDHL-370CDHL-450CDHL-590

    CDHT-370CDHT-450CDHT-590

    370 SCFM450 SCFM590 SCFM

    370450590

    CDHE-750CDHE-930CDHE-1130

    CDHL-750CDHL-930CDHL-1130

    CDHT-750CDHT-930CDHT-1130

    750 SCFM930 SCFM1130 SCFM

    7509301130

    CDHE-1350CDHE-1550CDHE-2100

    CDHL-1350CDHL-1550CDHL-2100

    CDHT-1350CDHT-1550CDHT-2100

    1350 SCFM1550 SCFM2100 SCFM

    135015502100

    CDHE-3000CDHE-4100CDHE-5400

    CDHL-3000CDHL-4100CDHL-5400

    CDHT-3000CDHT-4100CDHT-5400

    3000 SCFM4100 SCFM5400 SCFM

    300041005400

    lbairagiText Box950210462-9.4.2-MAN-4

  • 2

    2. Receiving, Moving, Unpacking

    2.1 Receiving: This shipment has been thoroughly checked, packed and

    inspected before leaving our plant. It was received in good condition by the carrier and was so

    acknowledged. Check for visible loss or damage. If this shipment shows evidence

    of loss or damage at time of delivery to you, insist that the carriers agent make a notation of this loss or damage on the delivery receipt.

    2.2 Moving:CAUTION: Use lifting lugs or forklift. Do not lift equipment by piping.

    2.3 Unpacking: Check for concealed loss or damage. When a shipment has been

    delivered to you in apparent good order, but concealed damage is found upon unpacking, notify the carrier immediately and insist that his agent inspects the shipment.

    Fifteen days from receipt of shipment is the maximum time limit for requesting such inspection.

    Concealed damage claims are not our responsibility as our terms are F.O.B. point of shipment.

    1. General Safety Information

    1.1 Pressurized Devices This equipment is a pressure-containing device. Do not exceed maximum operating pressure as shown on the

    equipment serial number tag. Verify that equipment is fully de-pressurized before performing

    service or maintenance functions.

    1.2 Electrical: This equipment requires electricity to operate. Install equipment in compliance with national and local electrical

    codes. Standard equipment is supplied with NEMA 4,4X electrical

    enclosures and is not intended for installation in hazardous environments.

    Disconnect power supply to equipment when performing any electrical service work.

    1.3 Breathing Air: Air treated by this equipment may not be suitable for breathing

    without further purication. Refer to OSHA standard 1910.134 for the requirements for

    breathing quality air.

    1.4 Noise:CAUTION: Do not operate dryer without mufflers installed.

    1.5 High Velocity Air:CAUTION: Do not stand near mufflers during tower depressurization.

  • 3

    3. Description

    3.1 Dryer Function Dual tower regenerative desiccant dryers are an economical

    and reliable way to dry compressed air to dew points below the freezing point of water (dew points as low as -150F (101C) [1 ppb @100 psig, 7.0 kgf/cm2] are possible) or reduce the moisture content of compressed air when used in critical process applications.

    These dryers continuously dry compressed air by using two identical towers, each containing a desiccant bed. While one tower is on-stream drying, the other tower is off-stream being regenerated (reactivated, i.e., dried out). The towers are alternated on- and off-stream so that dry desiccant is always in contact with the wet compressed air. In this way a continuous supply of dry air downstream of the dryer is possible.

    Desiccant dryers lower the dew point of compressed air by adsorbing the water vapor present in the compressed air onto the surface of the desiccant. Desiccant is a highly porous solid containing extensive surface area.

    Adsorption occurs until the partial pressure of the water vapor in the air and that on the surface of the desiccant come into equilibrium. As adsorption occurs, heat is released (referred to as the heat of adsorption) and is stored in the bed for use during regeneration.

    Desiccant is regenerated by driving off (desorbing) the water collected on its surface. Pressure-swing (also called heatless or heater-less because no outside heat is added) dryers regenerate by expanding a portion (approximately 14 -15% at 100 psig, 7 kgf/ cm2) of the dried air to atmospheric pressure. This swing in pressure causes the expanded air to become very dry (have a very low vapor pressure). This very dry air (called purge air) plus the stored heat of adsorption allows the moisture to desorb from the desiccant. The purge air then carries the desorbed water out of the dryer.

    3.2 Automatic Purge Saving SystemFeatured with the Level 2 Controller, the Automatic Purge Saving System is designed to save energy (purge air) when pressure-swing dryers are operated at reduced loads.The patented Purge Saving System operates by monitoring the changes in temperature within the desiccant beds. These changes in temperature are the result of heat (thermal energy) that is released when a bed is on-line drying (heat of adsorption), and the heat that is used when a bed is off-line being regenerated (heat of desorption). The magnitude of these changes in temperature is an indirect measure of the water vapor content in the air being dried. This information is used to determine the time a tower stays on line during the drying cycle.

  • 4

    3.3 Description of Operation Dryer

    3.3.1 Models 40 to 3000 w/ Shuttle Valve

    (Refer to Fig. 3-1a.) Compressed air ows through inlet shuttle valve (3) to tower (4A) where the air is dried. After the air is dried it ows through outlet shuttle valve (5) and then to the dryer outlet. A portion of the dry air, the purge stream, branches off from the main air stream prior to the outlet. The purge stream ow rate is controlled by the adjustable purge rate valve (6) and the two purge orices (7).

    The purge ow, which has been throttled to near atmospheric pressure, is directed to tower (4B). As the purge ow passes over the desiccant in tower (4B), it removes the water vapor, which was deposited there while the tower was on-line drying. The purge air then passes through purge and repressurization valve (9B) (normally closed) and purge mufer (10B) to the atmosphere.

    After regeneration, purge and repressurization valve (9B) (normally closed) closes allowing tower (4B) to repressurize slowly. Adequate repressurization time is allowed so that tower (4B) is fully repressurized before tower switchover. After a controlled time period, purge and repressurization valve (9A) (normally closed) then opens. This causes the inlet and outlet shuttle valves to shift, directing the air ow through tower (4B).

    (Refer to Fig. 3-1b.) Tower (4B) is now drying the main air stream while tower (4A) is being regenerated by the purge air stream. The operation of the purge and repressurization (normally closed) valves is sequenced by the control system located in the electrical enclosure.

    8. Safety Valve9. Purge and Repres- surization Valves10. Purge Mufflers11. Moisture IndicatorA Left Tower SuffixB Right Tower Suffix

    TOWER 4B REGENERATING

    4BTOWER

    Purge StreamProcess Stream

    1. Tower Pressure Gauges2. Purge Pressure Gauge3. Inlet Shuttle Valve4. Desiccant Drying Towers5. Outlet Shuttle Valve6. Adjustable Purge Rate Valve7. Purge Orifices

    9A

    FIGURE 3-1aTOWER 4A DRYING

    INLET

    TOWER4A

    1

    76 2

    OUTLET

    5

    8

    9B

    10B

    1

    7

    9A

    TOWER 4B DRYING

    TOWER4A

    INLET

    FIGURE 3-1bTOWER 4A REGENERATING

    1

    76

    18

    27

    9B

    4BTOWER

    10A

    10B10A

    11

    511

    OUTLET

    3

    3

  • 5

    3.3.2 Models 4100 to 5400 w/ Check Valves

    (Refer to Fig. 3-2a.) Compressed air ows through inlet switching valve (3A) (normally open) to tower (4A) where the air is dried. After the air is dried it ows through outlet check valve (5A) and then to the dryer outlet. A portion of the dry air, the purge stream, branches off from the main air stream prior to the outlet. The purge stream ow rate is controlled by the adjusta

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